August 7, 2017
By cancercurehere
with Comments Off on Interferon alpha (IFNA) genes code for proteins with important signaling functions

Interferon alpha (IFNA) genes code for proteins with important signaling functions during the innate immune response. For the second control, GENECONV was rerun on IFNA alignments after those sequences harboring fragments with a significant signal for gene conversion were removed. If all fragments that underwent a gene conversion event had been identified previously then this repeated analysis should not identify new fragments. 2.4. Detection of whole gene conversion Serendipitously, the 5 non-coding region of IFNA genes from the chimpanzee, dog, human and rhesus macaque genome contained a copy of the conserved repeat element MER106B. The most parsimonious explanation for such a coordinated relationship of MER106B with IFNA genes is usually that this repeat element was duplicated along with the gene sequence during the growth of the gene family. Therefore, evidence of whole gene conversion was identified by locating significant incongruence between the IFNA and MER106B phylogenetic trees, where discordant clades had high bootstrap support (>75) in each tree. Bootstrapped ML phylogenetic trees were constructed from IFNA gene and MER106B repeat element alignments using the methods and parameters already described. To maximize the MER106B alignment used for phylogenetic reconstruction, HsaMER2, PtrMER2 and MmulMER2 were removed because they represent a small fragment of the complete MER106B repeat element. Correspondingly, their gene equivalents (HsaIFNA2, PtrIFNA2 and MmulIFNA2) were also removed from the IFNA alignment to facilitate straightforward comparison of the two trees. PtrIFNA8 was removed from analysis since it was a pseudogene in the chimpanzee genome (see supplemental material for more details). 2.5. Synteny evaluation Advanced PipMaker (http://pipmaker.bx.psu.edu/cgi-bin/pipmaker?advanced) was used to align both genic and intergenic regions of the chimpanzee and rhesus macaque IFNA gene family locus to the human locus (Schwartz et al., 2000). Dot plots were obtained using and options. All other parameters were set to their defaults. 3. Results and discussion 3.1. Eutherian IFNA phylogenetic analysis Pestka et al. (2004) recently performed a phylogenetic analysis of all classes of Type I IFN, which provided a good starting point for examining the evolution of eutherian IFNA genes. We have improved upon their phylogenetic analysis of IFNA genes by: (1) using sequenced genomes to fully characterize IFNA gene families for chimpanzee, doggie, rat and rhesus macaque (Physique 1), (2) removing allelic variants, erroneous sequences and duplicate genes, (3) adding new IFNA gene sequence data for the cat (family (Jurka et al., 1996) and thus transposition is unlikely to have resulted in the ubiquitous presence of the MER106B element in species that have diverged more recently (i.e. human, chimp and rhesus macaque). These observations made it possible to identify instances of whole gene conversion as bootstrap supported differences in topology between the MER106B repeat element and IFNA gene trees IL1-BETA (Physique 4). Physique 4 ML phylogenetic trees constructed using the HKY85 substitution model of (A) MER106B repeat elements associated with (B) IFNA gene sequences. Sequences in strong represent those whose topology is different between the two phylogenetic trees and thus indicative … Todokoro et al. (1984) hypothesized that this similarity exhibited by HsaIFNA1 and 13 Nimorazole manufacture was the result of recent whole gene conversion and the primate clade of IFNA1 and IFNA13 sequences provides the best evidence of whole gene conversion in our study. Prior gene synteny analysis established that IFNA1 and 13 were present in the MRCA of humans, chimpanzee and rhesus macaque, and thus should cluster on a gene-specific basis (Physique 3). Such gene-specific clustering is usually confirmed in this clade with high bootstrap support when considering phylogenies of the MER106B element (Physique 4A). However, the IFNA gene phylogeny for this clade (Physique 4B) depicts bootstrap supported species-specific clustering such that HsaIFNA1 clusters with HsaIFNA13, and MmulIFNA1 with MmulIFNA13. The most parsimonious explanation is that whole gene conversion events have homogenized these gene sequences within species. Whether PtrIFNA1 and 13 have been affected by a whole gene conversion event is less clear. Another way to demonstrate whole gene conversion is usually to apply GARD to the concatenated sequences of the MER106B repeat element and IFNA gene sequences for IFNA1 and 13 from human, chimpanzee and rhesus macaque. If the only supported recombination breakpoint falls around the boundary between the MER106B repeat elements and the IFNA genes, then partial gene conversion in either the repeat element or the gene can be ruled out as statistically unlikely. Indeed, the only topological change is usually observed at the variable site nearest this boundary (AICc improvement of 123, KH Nimorazole manufacture p-value <0.01), which separates gene-specific (exhibited by Nimorazole manufacture MER106B) from species-specific (exhibited by IFNA) clustering (data not shown). Phylogenies for the IFNA gene and MER106B.